Amplification, rearrangement, and elevated expression of c-myc in the human prostatic carcinoma cell line LNCaP

We have investigated the structure and expression of the c-myc proto-oncogene in DNA isolated from the immortal cell line LNCaP. This cell line was derived from a lymph node metastasis of human prostate cancer. Msp I digest of LNCaP DNA when hybridized to a human c-myc probe showed a 1.45 kb band of intensity about two-fold greater than that observed in normal lymphocytes. In addition, the LNCaP cells contain rearranged and amplified c-myc structures which are not present in normal lymphocytes. Quantitation of these bands by scanning densitometry is consistent with an approximately 10-fold amplification of c-myc. To determine whether this amplification was accompanied by increased expression, RNA was isolated from these cells and compared to RNA isolated from a control cell line in which c-myc was not amplified. Northern blot analysis showed that the RNA transcripts from LNCaP cells were approximately 50-fold higher. Although androgens modulate the cell growth of LNCaP, there was no change in the level of c-myc RNA transcripts in serum-free medium in the presence or absence of androgens. Further investigation to determine whether altered structure, amplification, and overexpression of c-myc constitute a common characteristic of metastatic human prostate cancer might prove profitable in understanding this disease.